Fix a shader generation bug.
A small political correctness change to the shader builder.
Initial work on adding support for specifying animation segments via the model editor.
More work on adding support for animation segments to models.

This commit changes the serialized format of model definitions.
Add initial support for playing an animation sequence in the model editor.
Improve animation playback of models in both the editor and C++ side.
Add support for playing model animation segments via the scripting environment.
Cleanup.
Temporarily disable the Animation Sequences panel in the model editor.
A few improvements to animation sequences.
Add support for animation sequences to the scripting environment.
Renaming to make things a bit clearer.
A temporary fix for an import bug.
Additions and fixes to the animation system.
First phase for improving model importing.
Remove useless constructor.
Add mesh names to the serialized format of model definitions.
Have the name of a mesh actually get set on import...
More improvements to models.

Reloading of materials is broken with this commit.
Fix a material reloading issue for models introduced by the previous commits.